In-flight aircraft engine propulsor blade deicing is necessary because the formation of ice on the blades decreases the amount of engine thrust. Electrical heating elements attached to the blade are used to heat the blade surface, thereby melting ice which forms thereon. The ice is thrown from the blade by the centrifugal force generated by the rotating propulsor.
The elements are comprised of a relatively thin, continuous, resistive metallic material (foil) which is laid out into a pattern and fixedly attached to a sheet of nylon which is fixedly attached to a sheet of neoprene, thereby forming a blade heater which is bonded to the blade. The resistive elements generate heat when electric power is applied.
Power for the blade heater comes from an aircraft electrical generator. Since it is desirable to decrease the cost and size of the generator, it is desirable to minimize the amount of power drawn by the blade heater while still effectively deicing the blades The power consumed by the blade heater is reduced by reducing the size of the heater so that only the radially inward most portion of the blade is heated. The centrifugal force at the radially outward most portion of the blade is sufficient for deicing without applying heat. Furthermore, since the majority of ice formation occurs at the leading edge (i.e. the edge of the blade which turns into the ambient air), the size of the heater, and hence the power consumed, can be further reduced by having the heater cover portions of the blade near the leading edge.
A further power reduction is obtained by decreasing the amount of heat generated by the radially outward most portion of the heater by decreasing the resistance of the radially outward most elements. The centrifugal force, which throws ice from the blades, is greater at the radially outward most portions so that less heat is required.